1. Field of the Invention
The present invention relates to an antitheft device, a monitoring device and an antitheft system and, more particularly, to an antitheft device for preventing vehicle theft, a monitoring device for monitoring a vehicle and an antitheft system.
2. Description of the Relevant Art
Both the number of cases and the incidence of theft such as vehicle theft and theft from a vehicle are tending upward. Therefore, in recent years, various antitheft devices for preventing vehicle theft (including theft from a vehicle) have been proposed (for example, Japanese Kokai No. 1999-7561 and No. 2000-231691).
FIG. 29 is a block diagram schematically showing the principal part of an antitheft system comprising a conventional antitheft device. Reference numeral 1 in the figure represents an antitheft device, comprising a microcomputer 2 including a CPU 3, and a ROM 4 and a RAM 5, an EEPROM 6 in which an ID code preset for each vehicle, and a receiving section 7 for receiving signals (signals including an ID code) sent from a portable transmitter 13 an authorized driver carries with him/her.
The microcomputer 2 is connected to a door open/closed state detection sensor 8 for detecting the open/closed state of doors, a door locked state detection sensor 9 for detecting the locked/unlocked state of the doors, an intrusion detection sensor 10 for detecting intruding objects into a vehicle, an audible alarm generator 11 for generating an audible alarm and a communication device 12 for reporting to the police, a security company or the like.
The microcomputer 2 sets or cancels an arming mode for being on the alert for vehicle theft and the like, based on a signal sent from the portable transmitter 13, the ID code stored in the EEPROM 6, the open/closed state of the doors and the locked/unlocked state thereof.
For example, when a proper ID code, or the ID code stored in the EEPROM 6 is received with all the doors locked, the arming mode is selected. On the other hand, when the proper ID code is received with all the doors unlocked, the arming mode is canceled.
When an intruder into the vehicle is detected by the intrusion detection sensor 10 with the arming mode set, the microcomputer 2 controls the audible alarm generator 11 so as to generate an audible alarm, or controls the communication device 12 so as to report the occurrence of vehicle theft to a security company or the like. Thus, by sounding an alarm or reporting to a security company or the like when an intruder into the vehicle was detected by the intrusion detection sensor 10, it appears to become possible to restrict damage to a minimum even if the damage was caused by vehicle theft or the like.
As a conventional intruder detection sensor, a vibration sensor for detecting breaking of glass and a sensor for ultrasonically detecting the motion of a person who intruded into the vehicle without authorization are exemplified, but there is a possibility that these sensors frequently cause errors in detection. For example, a cat walking on the vehicle roof or a person who passed by the vehicle might be detected as an intruder.
In order to reduce such errors in detection, the sensitivity of these sensors may be set lower, but the lower sensitivity might have the opposite effect of being incapable of detecting an intruder to be detected.
As described above, by sounding an alarm or reporting to a security company or the like when an intruder into the vehicle was detected by the intrusion detection sensor 10, it appears to become possible to minimize damage even if the damage was caused by vehicle theft or the like.
However, modi operandi of thefts have been sophisticated, for example, they wait for an alarm to stop, or they previously work for preventing an alarm from sounding. Therefore, antitheft devices having higher effects of crime prevention have been required. And it is also extremely important to appropriately monitor approaching objects toward the vehicle for the prevention of theft.